1. Field of the Invention
The present invention relates to the use of silicon carbide/aluminum nitride as a solid solution ceramic composite for use in armor, cutting tools, wear parts, nozzles, parts subject to high temperature, and similar articles subjected to severe impacts or abrasive action.
2. Description of the Prior Art
Cutler et al U.S. Pat. No. 4,141,740 discloses a refractory product formed as a solid solution from aluminum nitride, silicon carbide, and aluminum oxycarbide and the process for producing the refractory product. This patent is cited as background pertaining to the subject invention.
It is well known that silicon carbide ceramic faced armor systems are light weight and offer substantially better ballistics performance than that of monolithic metallic plates. The silicon carbide ceramic faced armor systems are better because the ceramics which are used have greater compressive mechanical properties, especially dynamic compressive yield strengths, than do the metals. These ceramics then cause the projectile to deform more than do the metals, either through plastic deformation and erosion, or through fracture. The penetration capabilities of the projectile is reduced by this increased deformation in two ways. Projectile plastic deformation and consequent erosion reduces the kinetic energy of a projectile through plastic flow and reduction in projectile mass. Alternately, a fractured projectile is essentially defocused; its impact footprint is increased which allows a large volume of the target material to work against the projectile.
While silicon carbide ceramic faced armor systems have performances which are known to be superior to most other systems, it is not presently used on light armored combat vehicles for two major reasons. The first is cost; the high performance silicon carbide ceramic materials now typically cost in the range of $50.00 to $100.00 per pound. Our Government is presently unwilling to pay the resulting high cost of an armor system utilizing these high cost ceramics for application to a light weight armored vehicle. The other reason is the typical poor multi-hit performance of silicon carbide ceramic systems caused by the highly brittle nature of the ceramic material. Silicon carbide ceramic faced armored systems are typically built with ceramic plates or "tiles". A ballistic impact on one tile is sufficient to fracture that tile such that it will not prevent a penetration if hit a second time. In addition, the impact into the first tile can often induce fracture of adjacent tiles, reducing their performance such that they will no longer prevent projectile penetration. Hence, the multi-hit performance, or number of projectiles that can be stopped at any given area is limited.